Removal of organic fluorine



Patented Oct. 15, 1946 REMOVAL OF ORGANIC FLUORINE Maryan I. Matuszak, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporationof Delaware No Drawing.

. r t 1 v a This invention relates to the treatment of organic materials to remove organic fluorine-containing compounds therefrom. In one general embodiment it relates to the removal from hydrocarbon materials of fluorine-containing organic compounds which are present in relatively minor amounts. In a more specific embodiment my invention relates to the removal of at least a major portion of organically bound fluorine from hydrocarbon materials containin organically bound fluorine in an amountnot greater than about 2 per cent by weight, and often in an amount not greater than about 0.1 to about 0.5 per cent by weight. The invention is particularly applicable to such fluorine removal as carried out with the aid of naturally occurring minerals containing silica as an impurity.

In the manufacture of hydrocarbons by processes in which fluorine-containing catalysts are used, small proportions of organic fluorine-containing lay-products are often formed. Processes to which my invention may be generally applied involve the alkylation of relatively low-boiling hydrocarbons with oleflns, alcohols, ethers, alkyl halides, and the like, to produce higher-boiling hydrocarbons in the presence of catalysts comprising one or more such fluorine compounds as hydrofluoric acid, boron trifluoride, antimony trifluoride, complexes of these with other materials such as are formed by boron trifluoride and water,

various organic acids, alcohols, and acids of phosphorus. My invention may also be applied to processes wherein such low-boiling hydrocarbons are .isomerized in the presence of such catalysts. The exact nature and composition of the organiccontaining by-products which are formed and which are present as impurities in the desired product has not been definitely established, although they are believed to be predominantly alkyl and/or aryl fluorides, but it is known that they are not completely removed by washing the products with lkali solutions, and that they tend .to decompose at elevated temperatures such as those employed in fractional distillation of the products, thereby forming hydrofluoric acid which is corrosive, especially in the presence of moisture. In gases they may thus cause corrosion of han- 'dling equipment; in liquid motor fuel hydrocarbons they are undesirable for reasons that are obvious.

Two general methods of removing-such organic combined fluorine are available. One involves a decomposition of the same underconditions liberating free hydrogen fluoride, which is subsequently removed from the hydrocarbons by distillation Application January 3.1944, Serial No. 516,852

10 Claims. (01. 196-411 or otherwise. The other method involves treat ment with a solid porous. contact material under conditions binding the fluorine so that the treated hydrocarbon material is not only freed from a substantial part or all of the organically combined fluorine but is also recovered without being contaminated with free hydrogen fluoride. The latter process is described in the copending application of Frederick E, Frey, Serial Number 398,361, filed June 16, 1941, now U. S. Patent 2,347,945, issued May 2, 1944. Among the contact materials which may be used in such a process are those catalytically active for hydrogena-. tion and dehydrogenation reactions, preferably the oxides of various metals, such as the oxides of metals chosen from the group consisting of aluminum, titanium, zirconium, hafnium, thorium, vanadium, chromium, moIy-bdenumtungsen, uranium, manganese, iron, cobalt, nickel, or the like, alone or in admixture, synthetically produced or in naturally occurring forms such as ores. Due primarily to their low cost and availability, the naturally occurring ores are ordinarily used, and bauxite has been found to be particularly advantageous. Other naturally occurring oxides such as limonite, manganite, baddeleyite, brookite, brucite, diaspore, dysanalite, .gibbsite, goethite, heusmannite, huebnerite, ilmenite, lepidocrite, rutilefspinel', valentinite, etc., are also useful.

Unfortunately, natural contact materials of this type contain up to as, much as 20 per cent by weight Or more of siliceous material, most gener ally silica, as an impurity. In'actual practice, such silica apparently reacts with hydrofluoric acid believed to be formed by decomposition of the organic fiuorinecompounds before such'hydrogen fluoride becomes bound by the porous contact material. At anyrate, the formation of silicon tetrafluoride occurs. This silicon tetrafluoride is highly objectionable because it contaminates the hydrocarbon material, and because contact of it with moisture produces hydrofluoric acid, Whichis exceedingly corrosive, and at the same time deposits gelatinous silicic acid which accumulates until the equipment is plugged. Moreoventhe loss of fluorine, in the form of silicon tetrafluoride, is economically undesirable.

An object of this invention is to effect removal of organically combined fluorine from hydrocarbon'materials containing the same.

Anotherobject is to eifect substantially complete removal of fluorine from hydrocarbon fluids containing organic fluorine compounds as impurities.

tion will be apparent, to one skilled: intheart from the accompanying disclosure and discussion.

According to this invention, in preferred-embodiment, a small proportion of ammonia, usually less than 1 per cent by weight, and preferably not more than approximately the. stoichie-J ometric equivalent of the fluorine, such asziorexample 0.001 to 0.01 per cent by weight, is added. to the hydrocarbon material before contacting with the silicon-containing bauxite or other contact material of the nature described. Hydro fluoric acid present in the hydrocarbon material or formed from the organicfluorine is" believed to react with the ammonia to form ammonium fluoride and/or ammonium acid fluoride, wherebyj;it is prevented from forming silicon tetrafiuorid'e: Furthermore, any silicon tetrafiuoride which maybe fbrmedis converted to" ammonium fiiiosiiicate," which is relatively less volatile; so

thafthe" hydrocarbon" material remains free from this objectionable compound. The ammonium salts. are retained by the contact mate'- rial'. The addition of ammonia: to. the hydrocarb'on-st'ream has'the-practical advantages that pretreatment of'the bauxite is" unnecessary and -'--'I that" the ammonia can be added in' controlled proportion in accordance with need as shown by analysis of the effluent hydrocarbon material. Any ammonia in' the hydrocarbon stream inexcess of that required for reaction with'hydrofiuoricacid' and/or silicon tetrafluoride; appears to be adsorbed by the bauxite and/or the. deposited ammonium salt' or salts, so. that the diluent hydrocarbon stream is' ammonia-free. When the bauxite has become spent; the passage of' hydrocarbon materials is interrupted; andthe bauxite is revivified" or" replaced.

It will be appreciated that natural ores containing relatively high proportions of silica. are more readily available and much cheaper. than thosehaving an unusually lowsilica: content. Such advantages of high-silica ores are even more pronounced when compared with synthetically produced materials. My' invention may be appli'ed to treatment with materiais of' lower high silica-content to advantage, and the'choice of particular" contact" material will be largely a matter of economic consideration.

When'the'spent contactmass'isi to be revivified, itis-heated to-an elevated temperature at which ammonia and ammonium salts are volatilized'. The vol'atilizationmay be aided by' a flowing. atmosphere of an" inert carrier gas. Usually, volatili'zat'i'onv of all the ammonia and ammonium salts need not. be practiced. During the. revivification some. silica may be removed as silica tetrafiuoride. and/or ammonium.fluosilicate;. in. fact, insome instances, after revivificationthebauxite or.-other catalyst: may contain: so little: silica that subsequent use of. itrmay bemadeeintheordinary manner: without use. of ammonia. The gases: and fumes; eifluent from the revivification. may be passed tov a. recovery step for: recovery. of ammonia and/or other desired compounda.

monia thus recovered may be reused in the process of the present invention.

In carrying out a treatment in accordance with my invention, the hydrocarbon material, containing a small added proportion of ammonia, is passed in the liquid or vapor phase, preferably in the liquid phase, through the contact mass, which is preferably bauxite, at a space velocity of approximately 1 to 10 volumes of liquid per volume of contact mass per hour and at a temperature-in the. range between about 100 and 350 F. The pressure on the hydrocarbon material, although not critical, is preferably between about*- and 500 p. s. i. (pounds per square inch), and is chosen to give vapor phase, mixed phase, or liquid phase operation as desired.

In order to illustrate certain features of my invention, the following examples are offered. It

will of course be understood that the data given are only exemplary in nature, and hence are not to be. so construed as to unduly limit the invention'.

In an exploratory'experiment, 03 gram of ammoniawas mixed with 48.5 grams of n-butane containing 0.069 percent by-weight of silicon tetrafiuoride- After-the mixture had stood overnight',.the: butane contained only 0.011 per cent by-weightofsili-con tetrafiuoride; indicating that 84' per cent of the silicon tetrafiuori'cl'e had been converted to" compounds oflower volatility byreaction: with the ammonia.

In another exploratory experiment, a stream of n-butane containing'0.038 per cent by weight of ammonia waspassed through spent bauxite fromthe bauxite treater of a commercial hydrofiuoric. acid alkylation plant at a space velocity of 1.4 liquid volumes per volume of catalyst per hour and at a temperature of'180' F; After ammonia amounting to 3.4 percent by weight of the used bauxite had been adsorbed, a stream of'nbutane containing 0.0025 per cent by weight of silicon'tetrafiuoride was passed through the ammonia-containing bauxite at aspace velocity of 1.8lto 2.3 volumes of 'liquid pervolume of contact mass per hour. Substantially complete removal of the silicon tetrafiuoride. occurred.

In an illustrative specific example, a debutanizer overhead eflluentfrom the hydrofluoric acid alkylation of isobutane with butenes is mixed with 0.005 per cent by weight of ammonia, and the mixture is passed over bauxite; The rate of flow of the hydrocarbon is from 2 to 5 volumes of-hydrocarbon per volumeof' catalyst per hour; the-temperatureis'maintained at to 200 F.'.; the pressure is sufficient to maintain the hydrocarbon in the liquid phase. Substantially complete removal of the organic fluorine oc.curs;.and the efiluent hydrocarbon material is free from silicon tetrafluoride. When spent, the contact mass is heated in a stream of gas, such as natural gas or butane, to remove ammonia and ammonium' compounds; which are collected and used for any suitable purpose. The revivified contact mass is suitable for re-use. Any ammonia obtained by the revivificationstep. isrecycl'ed. to the process.

It..will,readily, be, appreciatedthat. while certain-specific aspects. of the. invention have been described .inconsiderable; detail, the. invention is not to be so construed as to be unduly limited thereby, and various modifications. and embodiments; may be practiced, by one skilled'inv the art; by following. the teachings of the. present disclosure. without departing from the spirit thereof or from the scopeof'theclaims.

I claim:

1. The process of removing organic fluorine from hydrocarbon materials containing the same which comprises treating such hydrocarbon ma terials with a solid contact material comprising a metal oxide catalytically active for hydrogenation and dehydrogenation reactions and containing silica as an impurity, said treating being conducted in the presence of added ammonia un der conditions producing a hydrocarbon effluent of substantially reduced fluorine content and substantially free from silicon compounds.

2. The process of removing organic fluorine from hydrocarbon materials containing the same, which comprises treating such hydrocarbon materials with a naturally-occurring solid metal oxide contact material active for removal of organically combined fluorine from hydrocarbon materials and containing a minor amount of silica as an impurity, said treating being conducted in the presence of ammonia under conditions producing a hydrocarbon eiiluent of substantially reduced fluorine content and substantially free from silicon compounds.

3. A process for treating a hydrocarbon material to remove organically combined fluorine therefrom, which comprises subjecting a hydrocarbon material, containing a minor quantity of organically combined fluorine and also containing ammonia in an amount substantially stoichiometrically equivalent to the fluorine content thereof, to the action of a naturally-occurring solid metal oxide contact material active for re moval of organically combined fluorine from hydrocarbon materials and containing a minor amount of silica as impurity, under conditions such that extensive chemical changes in said hy- 5. The process of claim 3, wherein said nat urally-occurring solid metal oxide contact ma terial is bauxite.

6. The process of claim 3, wherein said naturally-occurring solid metal oxide contact ma terial is an oxide of an iron-group metal.

'7. The process of claim 3, wherein said naturally-occurring solid metal oxide contact material is iron oxide.

8. The process of claim 3, wherein, when said contact material becomes incapable of removing fluorine to a desired extent, said contact material is heated in a stream of inert gas to an elevated temperature adequate to effect the vola' tilization of at least a portion of the ammonium compounds therefrom, and is then reused for said fluorine removal.

9. In a process for the removal of organically combined fluorine from a hydrocarbon material containing the same, wherein such a material is contacted with bauxite containing siliceous impurities under conditions such that extensive chemical changes in said hydrocarbon material itself are not efiected and such that the hydrocarbon effluent from said contacting is substantially free of such organically combined fluorine but normally contains volatile compounds of silicon and fluorine, the improvement which comprises admixing with such hydrocarbon material undergoing said contaoting a minor quantity of ammonia at least stoichiometrically equivalent to the fluorine content thereof.

10. The process of claim 9, wherein said hydrocarbon material contains not over about 2 per cent by weight of fluorine, is contacted in the liquid phase with bauxite at temperatures between about and about 350 F. at flow rates between about 1 and about 10 volumes per volume bauxite per hour, and in which a hydrocarbon efiluent from said contacting is'obtained substantially free from silicon and from fluorine.

MARYAN P. MATUSZAK. 

